Are you thinking of buiding it? It looks pretty similar to this:A Kilowatt Switching High Voltage Power Supply
Nice. Im interested because Im building a TIG welder along similar lines. I also have six 48V 30A telecomms PSUs that use a very close circuit but have active power factor correction.
Cheers Matt.

Are you thinking of buiding it? It looks pretty similar to this:A Kilowatt Switching High Voltage Power Supply
Nice. Im interested because Im building a TIG welder along similar lines. I also have six 48V 30A telecomms PSUs that use a very close circuit but have active power factor correction.
Cheers Matt.

Your Becnh is amazing, I liked it, Also your project construction is amazing,
I am in the process of building this supply for Audio Amplifier.

Are you thinking of buiding it? It looks pretty similar to this:A Kilowatt Switching High Voltage Power Supply
Nice. Im interested because Im building a TIG welder along similar lines. I also have six 48V 30A telecomms PSUs that use a very close circuit but have active power factor correction.
Cheers Matt.

This looks a lot like the prototypes that I were doing several years ago before I got into double sided PCB, SMD and careful control of parasitics. It's built like a 100KW supply but only intended for 1-2KW. Connecting things with wires point to point is ok for switching frequencies below 5Khz with slow semiconductors and low di/dt and dv/dt slopes, it's how industrial inverters are done.

But at higher frequencies, higher di/dt and dv/dt slopes are required for good efficiency, but they are not achievable reliably with wires and a point to point scheme because parasitic voltage spikes appear everywhere increasing stress on power transistors and diodes and ultimately causing the circuit to disturb itself due to EMI and fail.

The voltage drop across an inductor is V=L*di/dt. This rule applies to the parasitic inductances on every wire, PCB track and on every component lead too. For example, in the class D amplifier that I'm finishing I use the parasitic L*di/dt drop across the source leads of the MOSFET to control turn on di/dt. The gate drive circuit does not allow 3V of drop to be exceeded on approx. 4nH, which translates into approx. 750A/us turn on slope. In other words, 66ns to start conducting 50A in each MOSFET, which nowadays is not crazy fast at all. Parasitic inductance of the source lead of a TO-220 case should be 7.5nH, but lead length and mounting style also counts a lot (the front side of the transistor is facing a ground plane too).

Note that, in a MOSFET or IGBT, the parasitic L*di/dt voltage drop across the source lead (and source PCB track or wire, every path shared with gate driver loop) appears in series with gate drive voltage. What could be the effect of this when connecting transistors with long leads to the PCB? (Particularly when you are not considering at all the parasitics involved in what you are doing ) I blew many transistors that way.

__________________
I use to feel like the small child in The Emperor's New Clothes tale

Its not my bench:-) and yes it is a bit wrong. especially the way he has the gate drive transformer located two feet away using twisted up telephone wire.

Just thought I would post it, he does give a good run down of the way he got over the problems. I am sure there are still many.

I recently got hold of a massive transistor stack capable of 400 or so amps. This thing is wrong. It at least uses current sharing resistors (they are darlingtons 1990 style) but each row of trannys is connected to each other in turn rather than a nice star type arrangement. Good job it was a prototype and has never been used:-)
It will after being reconfigured make a nice half bridge for my TIG welder project. I am glad I got it as the price of a pair or even multiple IGBTs to make up 200A or so is very expensive. Plus this will not see much over 400Hz so parasitics should not be a problem. This does not mean that I wont design it accordingly.

Micro, If you are serious about building a switcher start with a smaller one. Modify an old PC supply and play about. At least its cheap. At the >1Kw level you start getting into expensive semiconductors and one blow up is enough to ruin a project and it will blow up. Switchers are hard to design and build, read as much as you can. Many of the application notes by the suppliers are more useful than stuff on the general web, but most of all build something smaller along similar lines first.

Cheers Matt.

Make sure you use an isolation transformer!!. Also watch out for the input caps. 380 odd volts will kill. Keep safe.

Last edited by Matt BH; 3rd December 2009 at 11:39 PM.
Reason: caution

Micro, If you are serious about building a switcher start with a smaller one. Modify an old PC supply and play about. At least its cheap. At the >1Kw level you start getting into expensive semiconductors and one blow up is enough to ruin a project and it will blow up. Switchers are hard to design and build, read as much as you can. Many of the application notes by the suppliers are more useful than stuff on the general web, but most of all build something smaller along similar lines first.

Cheers Matt.

Thanks for the note. and I already played with half bridge 900W, and blow up about 50 Mosfets, and already I worked into fixing SMPS for amplifiers for 12 years, and I know what I am doing, so don't worry

I am no longer working at the 2KW SMPS alone (since I need a lot of information's cannot find for free), there are 2 engineers engaged into this project (Fully PAID), I don't think I will fail, since this project will cost about 3000 US$ between parts and design

The transformer designed at percussion-Inc, PCB in India. All parts from RS.
Why not to make that supply reality?